The present invention relates generally to electrical leads for connecting implantable medical devices with selected body tissue to be stimulated by such devices, and more particularly to techniques for providing a secure electrical and mechanical connection between an elongated conductor cable and a mating electrode.
It has been known that implantable defibrillation leads, especially transvenous leads, typically employ elongated coils as electrodes. These electrode coils are coupled at one or both ends to an elongated conductor extending through the lead body to the electrode. Transvenous pacing leads, cardiac ablation catheters and other electrode bearing leads and catheters may also employ coil electrodes. Over the years, quite a large number of different mechanisms for interconnecting coil electrodes and conductors have been proposed including welding, crimping, and swaging. It is desirable that such connections between the conductor and the electrode provide a highly reliable electrical connection, with good mechanical properties including high tensile strength. It is also desirable that such connections allow for the lead assembly itself to retain a high degree of tensile strength through the area of the electrode:
Typically, conductors in commercially marketed pacing and defibrillation leads have taken the form of single or multifilar wire coils. However, there has been a high level of interest recent in pacing and defibrillation leads employing stranded wire conductors such as cables, instead of coiled wire conductors. Such stranded conductors present a new set of requirements for interconnection with electrode coils, if the above described design goals are to be accomplished. The present invention relates to this more recent lead technology.
Typical of the prior art in this regard is U.S. Pat. No. 5,591,142 to Van Erp which discloses encasing wires within a metal sleeve and U.S. Pat. No. 5,676,694 to Boser et al. which discloses laser welding an electrode to a sleeve and covering the electrode with a polymeric sleeve.
Other patents, as follows, disclose positioning wires outside of a conductor with subsequent mounting thereon of an electrode or the like:
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
The present invention relates to an implantable medical electrical lead made by forming a generally radially directed bore extending between each lumen of an elongated lead body having a plurality of internal longitudinally extending, circumferentially spaced lumina. The bores are located at longitudinally and circumferentially spaced locations and an elongated conductor cable is then drawn into and through each lumen of the lead body such that a terminal end thereof projects through and beyond an associated one of the bores. A metallic tube is slidably attached onto each conductor cable adjacent the cable""s terminal end, then is firmly joined to its associated conductor cable. Thereupon, each metallic tube is affixed, as by welding, preferably, by laser welding, to an associated one of a plurality of tubular electrodes coaxial with, and overlying, the lead body at longitudinally spaced locations. In one instance, the tubular electrode may be a ring electrode with the lead body connected to a pacemaker. In another instance, the tubular electrode may be a shock coil electrode with the lead body connected to a defibrillator.
It has been a great challenge to electrically and reliably connect a small multi-strand conductor cable (for example: 0.006 inch cable consisting of 7 wires, in which the wire O.D is 0.002 inches) to a ring electrode or a multifilar shock coil electrode. Being of such small size, the connection is very difficult one to make and, once made, is very fragile and unlikely to endure for a multi-lumen lead body, where the cable is brought out from the inner lumen and attached to the electrode. The invention described herein, however, provides an easy, practical and reliable connection between such a small cable and an electrode on a multi-lumen lead body.
At the location of the electrode on the multi-lumen lead body, the cable end is drawn out from the inner lumen via a small pre-pierced hole on the multi-lumen insulation lead body tubing. A metallic tube is installed over the cable located outside the lead body. The metallic tube (such as Pt/Ir or MP35N) is crimped or compressed or otherwise operated upon to provide a permanent connection between the cable and the metallic tube. The ring electrode for a Brady lead or a shock coil electrode is then installed over the lead body and the crimped tube. Welding, and preferably laser welding, is used to provide permanent electrical connection between the electrode and the crimped tube.
A primary feature, then, of the present invention is the provision of an improved electrical lead for connecting an implantable medical device with selected body tissue to be stimulated by such device.
Another feature of the present invention is the provision of such an electrical lead which can be readily manufactured from commonly available materials.
Still another feature of the present invention is the provision of such an electrical lead which can be inexpensively manufactured while maintaining the performance achieved by much more expensive electrode designs.
Yet a further feature of the present invention is the provision of a technique for providing a secure electrical and mechanical connection between an elongated conductor cable and a mating electrode.
Still a further feature of the present invention is the provision of such an electrical lead constructed by drawing an elongated conductor cable first through each lumen of an elongated multi-lumen lead body, then into and through a generally radially directed bore extending between each lumen and the outer peripheral surface of the lead body, the generally radially directed bores being located at longitudinally spaced locations, such that a terminal end of the cable projects through, and beyond, an associated one of the generally radially directed bores, then slidably attaching a metallic tube onto each conductor cable adjacent its terminal end, then firmly joining each metallic tube and its associated conductor cable, and then affixing each metallic tube to an associated one of a plurality of tubular electrodes coaxial with, and overlying, the lead body at longitudinally spaced locations.
Yet another feature of the present invention is the provision of such an electrical lead wherein each electrode is affixed to its associated metallic tube by welding and, preferably, by laser welding.
Still another feature of the present invention is the provision of such an electrical lead wherein each tubular electrode is a ring electrode; and wherein the lead body is connected to a pacemaker.
Yet another feature of the present invention is the provision of such an electrical lead wherein each tubular electrode is a shock coil electrode and wherein the lead body is connected to a defibrillator.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.